The present invention relates to improvements in security locking devices, and in particular to a novel and improved lock of the padlock type.
The term "padlock" is used to define a portable and removable lock, the most common of which is a removable lock having a shackle which can be passed through a hasp, staple or link and then secured to fasten a movable member to a fixed member. Padlocks of this shackle type are finding increasing use for high security applications such as for locking store front gates which are presently in common use, and for locking tool lockers used by utility companies for storing expensive tools and equipment.
It has been found by wide experience that padlocks of the shackle type which are available today are subject to inherent weaknesses when under physical attack. One basic weakness is in the exposed shackle which can be easily cut with commonly available tools. In addition, frequent assaults upon the locks have shown that the lock itself can be used as a tool for easily destroying the hasp or link to which it is attached by torque or leverage force. The security function of conventional padlocks can therefore be easily defeated by burglars or other unauthorized persons.
It is the principal object of the present invention to substitute for conventional padlocks a new type of portable and removable locking device which is herein referred to as a "concealed post lock", which is much more resistant to physical attacks than the strongest available conventional padlocks which have exposed shackles.
Another object of the invention is the provision of a concealed post lock which is formed of a large and thick metal head containing the lock cylinder and a locking post or stem projecting from the head and concealed behind the surface which is locked, so that the post is not exposed to physical attack, and the locking parts are protected by the structure to be secured.
Still another object of the invention is the provision of a concealed post lock of the character described in which the head is the only portion of the lock exposed to attack in the locked condition of the device, and in which the exposed head is of sufficient thickness and strength to protect the contained cylinder from destruction under even the most violent attack with commonly available tools.
Another object of the invention is to provide a concealed post lock of the character described in which the lock is brought to its locking position by inserting its post or stem through a hole in the object to be locked, and in such locking position the entire lock is rotatable so that it cannot be damaged or removed from effective locking condition by the application of torque forces.
Another object of the invention is the provision of a concealed post lock of the character described which has the advantage of being capable of installation in such a way that its enlarged head serves to block rotation or other movement of handles or levers on the door or other member being secured so as to prevent unauthorized operation of such handles or levers.
A further object of the invention is the provision of a concealed post lock of the type described which affords the convenience and flexibility of conventional padlocks, but at the same time is adapted to provide maximum security protection to such diversified applications as store front gates and industrial roll-up doors, tool boxes and lockers, trucks, machinery, and other security-sensitive spaces.